The present invention relates generally to combine harvesters and, more particularly, to improvements in the cleaning apparatus to permit a leveling thereof when the combine is operating under both transverse and fore-and-aft inclined operating conditions.
The operation of combine harvesters under non-horizontal conditions is less efficient than the operation of the combine on generally level ground because of the gravity induced movement of threshed grain in a downhill direction on the cleaning apparatus. This gravity induced movement creates an unbalanced loading of the cleaning mechanism and prevents a proper flow of air from a cleaning fan or series of fans through the threshed grain on the sieves to facilitate a removal of chaff and other debris. A lateral load unbalance shifts threshed grain to the side of the cleaning sieve and results in improper cleaning and higher grain losses. A fore-and-aft inclination of the sieves will result in the threshed grain being either retarded on the sieves or rushed toward the rearward end, which again results in improper cleaning action and/or high grain losses.
Attempts to maintain a combine cleaning apparatus in a horizontal orientation while the combine is operating under sidehill conditions can be found in U.S. Pat. No. 3,731,470 granted to G. K. Cornish et al. on May 8, 1973, and in U.S. Pat. No. 4,344,443 granted to C. R. J. DeBusscher on August 17, 1982. The apparatus disclosed in the Cornish patent provides a leveling of the entire frame of the combine through the operation of hydraulic cylinders to maintain the cleaning apparatus in a generally horizontal orientation. Since the entire combine is maintained in a level orientation, it was necessary to modify the connection of the crop harvesting header to the combine to permit a proper gathering of the crop material to be harvested.
The apparatus disclosed in the DeBusscher patent provides for a leveling of the entire cleaning mechanism, including the fan, about a longitudinally extending pivot axis; however, the DeBusscher mechanism does not provide for fore-and-aft leveling of the cleaning apparatus. The utilization of this leveling mechanism requires the use of a more complex, and therefore more expensive, main frame and drive train components. This complexity makes the elimination of a leveling mechanism to provide a stationary cleaning apparatus for use on flat land operations impractical. Furthermore, the DeBusscher mechanism is expensive to manufacture, is cumbersome to operate, results in an unnecessary shifting of major structural components and does not produce an overall leveling of the grain pan and chaffer sieve.